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System Contamination vs. Blockage in Coil

I have an Amana 13 Seer 2 Ton that has been installed in my house for three years. When I turned it on this summer I discovered that it was not properly cooling. I had three techs come out. The first and third provided the same explanation.

-The first tech that came out stated that there was contamination in the system from an improper installation of the unit by the builder's subcontractor. He recommended complete evacuation of the contaminated R410A and charge with new R410A.
-Builder's subcontractor stated that there is a possible blockage in coil, evacuate system, remove orifice, clean, replace coil if blockage is in coil. He planned on using same 410A that was originally in system.
-Third tech stated that contaminant in system, pressure does not indicate restriction in coil. Recommended recovery, flush, check piston, clean piston, replace filter drier, pull deep vacuum and recharge system.

I'm tempted to believe that there is a contaminant in system based on two techs stating this, but the builder's subcontractor repair recommendation concerns me because what if that is the problem?

I am hearing flashing outside when the unit has been running if that is of any help.

Any ideas, or thoughts on a similar situation you have encountered? I would love to have my house cool again. Thank you in advance.

The unit will shut off as its able to typically cool the house down two degrees as currently it's producing an 8 degree temperature variance from thermostat to return versus what I understand should be a 16-20 degree variance. On 90 degree days its constantly running with no chance of being able to keep up.

From the beginning,I thought it could never cool the house properly as it's a builder-installed unit, so I thought it was undersized. It would never cool off the 2nd floor of the two story house with a basement and has always run till the evening in the summer.

When I have Tech 3 out today to do the repair, is there a way he can check the coil when performing all this other work, just so I don't have another evacuation bill to pay?

The unit will shut off as its able to typically cool the house down two degrees as currently it's producing an 8 degree temperature variance from thermostat to return versus what I understand should be a 16-20 degree variance. On 90 degree days its constantly running with no chance of being able to keep up.

Okay, so until now, this unit cooled your house just fine, correct?

If so, it wasn't contaminated on Day One, at least the type of contamination that would cause a quick deterioration or failure of performance. I lean toward blockage or restriction that has occurred, which may also be a delayed onset of installer error, meaning it's possible nitrogen was not used during brazing operations, and now a chunk of carbon debris has blocked up the metering device. Could also be a plugged liquid line drier. Without the tech's data, it's just an experienced guess.

Yes it cooled the house just fine, except the top floor. Tech 3 thinks the unit is underpowered for size of house, which is why top floor never cooled correctly. Your solution to the problem is what Tech 3 is thinking. Any of the symptoms point to the evaporative coil being plugged as Tech 2 suggests? Any way for Tech 3 to check this? Would like to come in a little educated today when he comes out so that all bases get covered. Thank you!

Tech #3 should start the system, let it stabilize, and then gather superheat and subcooling readings, system operating pressures, return air wet and dry bulb temperatures, supply air wet and dry bulb temperatures, along with the outdoor air temperature during his data gathering efforts. He should record that on his invoice to you. He can also use the data to effectively troubleshoot your system.

He may also want to check for an excessive temperature drop through any liquid line drier installed on the system.